a:link{
    color:aqua;
    /* 链接未被访问 */
}

a:visited{
    color:purple;
    /* 链接已访问 */
}

a:hover{
    color: black;
    font-size: 20px;
    text-decoration: none;
    /* 鼠标悬停在标签时 */
}

a:active {
    color:pink;
    font-size: 120px;
    /* 链接被点击 */
}


.username:focus{
    border: 5px solid pink;
}

.password:focus{
    background-color:skyblue;
}

.checked:focus{
    background-color:skyblue;
    border-radius: 50%;
    /* -webkit-appearance: none; */
    /* 清楚默认样式 */
    width: 1000px;
    height: 500px;
}

/* div span:last-child{
    color: chartreuse;
}

ul li:nth-child(3) {
    font-size:100px;
} */

p::before {
    content: "[[";
    color: silverg;
}

p ::after{
    content: ">>>结尾";
    color: pink;
}

.aa{
    color: red;
}